Francis Bacon on Cryptology

The Advancement of Learning (1605) of the philosopher Francis Bacon is said to be the first book on cryptology in English. The first volume describes the significance of sciences and the second volumes systematically discusses the state of art of sciences and what is wanting therein, where ciphers are briefly mentioned.

Later, an enlarged edition in Latin, De Dignitate et Augmentis Scientiarum (Dignity and Advancement of Learning) (1623), was published. (According to the preface of Shaw, Bacon's philosophical works were all intended to be in Latin and those first written in English were afterwords put into Latin, with considerable improvements and corrections.) Its volumes 2-9 discuss the details of the second volume of The Advancement of Learning.

Excerpts from these works are provided below.

The Advancement of Learning (1605)

In The Advancement of Learning in English, the descriptions relevant to cryptography, including those of the famous biliteral cipher of Francis Bacon, are found in Volume 2, section XVI. Bacon divides the arts intellectual into four: (1) art of inquiry or invention; (2) art of examination or judgment; (3) art of custody or memory; and (4) art of elocution or tradition (XII(3)), which are discussed in sections XIII, XIV, XV, and XVI, respectively.

The following is the text of section XVI. The subsection most relevant to cryptography is XVI (6).

From The Advancement of Learning, section XVIXVI(1) There remaineth the fourth kind of rational knowledge, which is transitive, concerning the expressing or transferring our knowledge to others, which I will term by the general name of tradition or delivery. Tradition hath three parts: the first concerning the organ of tradition; the second concerning the method of tradition; and the third concerning the illustration of tradition.XVI(2) For the organ of tradition, it is either speech or writing; for Aristotle saith well, "Words are the images of cogitations, and letters are the images of words." But yet it is not of necessity that cogitations be expressed by the medium of words. For whatsoever is capable of sufficient differences, and those perceptible by the sense, is in nature competent to express cogitations. And, therefore, we see in the commerce of barbarous people that understand not one another’s language, and in the practice of divers that are dumb and deaf, that men’s minds are expressed in gestures, though not exactly, yet to serve the turn. And we understand further, that it is the use of China and the kingdoms of the High Levant to write in characters real, which express neither letters nor words in gross, but things or notions; insomuch as countries and provinces which understand not one another’s language can nevertheless read one another’s writings, because the characters are accepted more generally than the languages do extend; and, therefore, they have a vast multitude of characters, as many, I suppose, as radical words.XVI(3) These notes of cogitations are of two sorts: the one when the note hath some similitude or congruity with the notion; the other ad placitum, having force only by contract or acceptation. Of the former sort are hieroglyphics and gestures. For as to hieroglyphics (things of ancient use and embraced chiefly by the Egyptians, one of the most ancient nations), they are but as continued impresses and emblems. And as for gestures, they are as transitory hieroglyphics, and are to hieroglyphics as words spoken are to words written, in that they abide not; but they have evermore, as well as the other, an affinity with the things signified. As Periander, being consulted with how to preserve a tyranny newly usurped, bid the messenger attend and report what he saw him do; and went into his garden and topped all the highest flowers, signifying that it consisted in the cutting off and keeping low of the nobility and grandees. Ad placitum, are the characters real before mentioned, and words: although some have been willing by curious inquiry, or rather by apt feigning, to have derived imposition of names from reason and intendment; a speculation elegant, and, by reason it searcheth into antiquity, reverent, but sparingly mixed with truth, and of small fruit. This portion of knowledge touching the notes of things and cogitations in general, I find not inquired, but deficient. And although it may seem of no great use, considering that words and writings by letters do far excel all the other ways; yet because this part concerneth, as it were, the mint of knowledge (for words are the tokens current and accepted for conceits, as moneys are for values, and that it is fit men be not ignorant that moneys may be of another kind than gold and silver), I thought good to propound it to better inquiry.XVI(4) Concerning speech and words, the consideration of them hath produced the science of grammar. For man still striveth to reintegrate himself in those benedictions, from which by his fault he hath been deprived; and as he hath striven against the first general curse [i.e., Expulsion from the Garden of Eden] by the invention of all other arts, so hath he sought to come forth of the second general curse (which was the confusion of tongues [i.e., following the attempt to build the Tower of Babel]) by the art of grammar; whereof the use in a mother tongue is small, in a foreign tongue more; but most in such foreign tongues as have ceased to be vulgar tongues, and are turned only to learned tongues. The duty of it is of two natures: the one popular, which is for the speedy and perfect attaining languages, as well for intercourse of speech as for understanding of authors; the other philosophical, examining the power and nature of words, as they are the footsteps and prints of reason: which kind of analogy between words and reason is handled sparsim, brokenly though not entirely; and, therefore, I cannot report it deficient, though I think it very worthy to be reduced into a science by itself.XVI(5) Unto grammar also belongeth, as an appendix, the consideration of the accidents of words; which are measure, sound, and elevation or accent, and the sweetness and harshness of them: whence hath issued some curious observations in rhetoric, but chiefly poesy, as we consider it, in respect of the verse and not of the argument. Wherein though men in learned tongues do tie themselves to the ancient measures, yet in modern languages it seemeth to me as free to make new measures of verses as of dances; for a dance is a measured pace, as a verse is a measured speech. In these things this sense is better judge than the art:
"Caena fercula nostra
Mallem convivis quam placuisse cocis."
[I wish dishes of our dinner please guests rather than cooks.]
And of the servile expressing antiquity in an unlike and an unfit subject, it is well said, "Quod tempore antiquum videtur, id incongruitate est maxime novum." [What looks old in time is the newest because of its incongruity.]XVI(6) For ciphers, they are commonly in letters or alphabets, but may be in words. The kinds of ciphers (besides the simple ciphers, with changes, and intermixtures of nulls and non-significants) are many, according to the nature or rule of the infolding, wheel-ciphers, key-ciphers, doubles, &c. But the virtues of them, whereby they are to be preferred, are three; that they be not laborious to write and read; that they be impossible to decipher; and, in some cases, that they be without suspicion. The highest degree whereof is to write omnia per omnia; which is undoubtedly possible, with a proportion quintuple at most of the writing infolding to the writing infolded, and no other restraint whatsoever. This art of ciphering hath for relative an art of deciphering, by supposition unprofitable, but, as things are, of great use. For suppose that ciphers were well managed, there be multitudes of them which exclude the decipherer. But in regard of the rawness and unskilfulness of the hands through which they pass, the greatest matters are many times carried in the weakest ciphers.XVI(7) In the enumeration of these private and retired arts it may be thought I seek to make a great muster-roll of sciences, naming them for show and ostentation, and to little other purpose. But let those, which are skilful in them, judge whether I bring them in only for appearance, or whether in that which I speak of them (though in few words) there be not some seed of proficience. And this must be remembered, that as there be many of great account in their countries and provinces, which, when they come up to the seat of the estate, are but of mean rank and scarcely regarded; so these arts, being here placed with the principal and supreme sciences, seem petty things: yet to such as have chosen them to spend their labours and studies in them, they seem great matters.

The Dignity and Advancement of Learning, the enlarged Latin edition (1623)

The section XVI above is enlarged in volume VI of the Latin edition. The following is the "interpretation" by Wats. Judging from partial comparison with the Latin version, Wats appears to have tried to make it more readily understandable by supplying some words and restructuring the demonstration.

According to Shaw's preface, there were already a number of translations of Bacon's works in Latin but there were but few that tolerably express the sense and meaning of the author. In particular, Shaw says Wats' translation of De Augmentis Scientiarum "is by the Learned accounted low, flat, and incongruous; so as no way to give the Spirit, Vivacity, and Mind of the Author; or shew his Views in a tolerable Light."

Shaw's English version in turn is "to give a Methodical English Edition of his Philosophical Works, fitted for a commodious and ready Perusal". Shaw's method "is not that of a direct Translation; (which might have left them more obscure than they are; and no way suited this Design;) but a kind of open Version, which endeavours to express, in modern English, the Sense of the Author, clear, full, and strong; tho' without deviating from him, and, if possible, without losing of his Spirit, Force, or Energy." Shaw dropped some parts of the work but he refrained from abridging. (For example, in XVI (6), an explanation "we devised in our youth, when we were at Paris" and an extensive demonstration of the biliteral cipher were left out. Shaw also substituted an English sentence for a Latin sentence to illustrate Bacon's cipher.) At least in form, Shaw's version appears to be no more faithful than Wats'. Shaw's text can be found by following the link given in References below.

From The Dignity and Advancement of Learning in Latin (De Dignitate et Augmentis Scientarium), Volume VI
Wherefore let us come to CYPHARS. Their kinds are many as, Cyphars simple; Cyphars intermixt with Nulloes, or non-significant Characters; Cyphers of double Letters under one Character; Wheele-Cyphars; Kay-Cyphars; Cyphars of words [i.e. code]; Others. But the virtues of them whereby they are to be preferr'd are Three; That they be ready, and not laborious to write; That they be sure, and lie not open to Deciphering; And lastly, if it be possible, that they may be managed without suspition. For if Letters Missive fall into their hands, that have some command and authority over those that write; or over those to whom they were written; though the Cypher it selfe bee sure and impossible to be decypher'd, yet the matter is liable to examination and question; unless the Cypher be such, as may be voide of all suspition, or may elude all examination. As for the shifting off examination, there is ready prepared a new and profitable invention to this purpose; which, seeing it is easily procured, to what end should we report it, as Deficient. The invention is this: That you have two sorts of Alphabets, one of true letters, the other of Non-significants; and that you likewise fould up two Letters; one which may carrie the secret, another such as is probable the Writer might send, yet without perill. Now if the Messenger be strictly examined concerning the Cypher, let him present the Alphabet of Non-significants for true Letters, but the Alphabet of true Letters for Non-significants: by this Art the examiner falling upon the exterior Letter, and finding it probable, shall suspect nothing of the interior Letter. But that jealousies may be taken away, we will annexe an other invention, which, in truth, we devised in our youth, when we were at Paris: and is a thing that yet seemeth to us not worthy to be lost. It containeth the highest degree of Cypher, which is to signifie omnia per omnia, yet so as the writing infolding, may beare a quintuple proportion to the writing infolded; no other condition or restriction whatsoever is required. It shall be performed thus: First let all the Letters of the Alphabet, by transposition, be resolved into two Letters onely; for the transposition of two Letters by five placeings will be sufficient for 32. Differences, much more for 24. which is the number of the Alphabet. The example of such an Alphabet is on this wise.

An Example of a Bi-literarie Alphabet.

Neither is it a small matter these Cypher-Characters have, and may performe: For by this Art a way is opened, whereby a man may expresse and signifie the intentions of his minde, at any distance of place, by objects which may be presented to the eye, and accommodated to the eare: provided those objects be capable of a twofold difference onely; as by Bells, by Trumpets, by Lights and Torches, by the report of Muskets, and any instruments of like nature. But to pursue our enterprise, when you addresse your selfe to write, resolve your inward-infolded Letter into this Bi-literarie Alphabet. Say the interior Letter beFuge.

Example of Solution.

Together with this, you must have ready at hand a Bi-formed Alphabet, which may represent all the Letters of the Common Alphabet, as well Capitall Letters as the Smaller Characters in a double forme, as may fit every mans occasion.

An Example of a Bi-formed Alphabet.

Now to the interiour letter, which is Biliterate, you shall fit a biformed exteriour letter, which shall answer the other, letter for letter, and afterwards set it downe. Let the exteriour example be,Manere te volo, donec venero.

An Example of Accommodation.

We have annext likewise a more ample example of the cypher of writing omnia per omnia: An interiour letter, which to expresse, we have made choice of a Spartan letter sent once in a Scytale or round cypher'd staffe.Perditae Res. Mindarus cecidit. Milites esuriunt. Neque hinc nos extricare, neque hic diutius manere possumus.
An exteriour letter, taken out of the first Epistle of Cicero, wherein a Spartan Letter is involved.
The knowledge of Cyphering, hath drawne on with it a knowledge relative unto it, which is the knowledge of Discyphering, or of Discreting Cyphers, though a man were utterly ignorant of the Alphabet of the Cypher, and the Capitulations of secrecy past between the Parties. Certainly it is an Art which requires great paines and a good witt and is (as the other was) consecrate to the Counsels of Princes: yet notwithstanding by diligent prevision it may be made unprofitable, though, as things are, it be of great use. For if good and faithfull Cyphers were invented & practised, many of them would delude and forestall all the Cunning of the Decypherer, which yet are very apt and easie to be read or written: but the rawnesse and unskilfulnesse of Secretaries, and Clarks in the Courts of Princes, is such, that many times the greatest matters are Committed to futile and weake Cyphers.

The teachings here include the following:

A cipher should be easy to use; hard to decipher; and, if possible, free from suspicion.

One technique to avoid suspicion (what is called steganography today) is to use a true alphabet as well as non-significant alphabet.

A cipher of the highest degree is to signify omnia per omnia (i.e., signify anything with anything). Any object capable of twofold difference, such as bells, trumpets, lights and torches, and the report of muskets, may be used to convey information. (A concept of binary representation of digital technology today.)

Such insights were highly appreciated in John Wilkins' Mercury (1641) and John Falconer's Cryptomenysis Patefacta (1685).

Dissemination of Knowledge of Cipher

Francis Bacon was appointed Solicitor-General in 1607, Attorney-General in 1613, and at last Chancellor in 1617. In a trial in May 1616, when he was Attorney-General, he made a speech, which sounded as if he considered that use of ciphers by those other than princes or their ambassadors and ministers must be for the purpose of intrigues.

The trial was about poisoning of Sir Thomas Overbury and Bacon mentioned cipher in a speech for prosecuting the Earl of Somerset. While Bacon had published knowledge of cipher in The Advancement of Learning, there were still many who considered knowledge of cipher might be used for intrigues and thus its dissemination was against the security of the nation. Thus, authors such as Wilkins, Falconer, and Thicknesse all made an excuse of some kind or other about their publishing knowledge of cipher.

And this Friendship [between the victim and the accused] rested not only in Conversation and Business of Court, but likewise in Communication of Secrets of State. For my Lord of Somerset, at that time exercising the Office of Secretary provisionally, acquainted Overbury with the King's Pacquets of Dispatches from all Parts, Spain, France, the Low-Countries, &c. And this not by glimpses, or now and then, sent, sometimes open'd by my Lord, sometimes unbroken to Overbury, who perused, copied, registered them, made Tables of them as he thought good; so that I will undertake, the time was when Overbury knew more of the Secrets of State than the Council-Table. Nay, they were grown to such an inwardness, that they made a play of all the World besides themselves; and had Cyphers and Jargons for the King, the Queen, and all the great Men; things seldom used, but either by Princes and their Embassadors, and Ministers, or by such as work and practice against, or at least upon, Princes

Francis Bacon, (ed.) Peter Shaw (1733), The philosophical works of Francis Bacon. Methodized, and made English, from the originals, vol.2 (Internet Archive, relevant descriptions start at p.141; Speech at the trial above starts at p.384, the relevant descriptions being from p.387.

Francis Hargrave (ed.) (1776), A Complete Collection Of State-Trials And Proceedings For High Treason and Other Crimes and Misdemeanours Vol.1 (Google, the above trial being from XXIX and Bacon's speech being from the middle of Column 352, the relevant paragraph being in Column 354.)